Field Sobriety Test: The One Leg Stand Test

Law enforcement conducts the One Leg Stand test with a suspected drunk driver

Police officers use a battery of tests called field sobriety tests (FSTs) to determine whether the driver of a vehicle is impaired and to develop probable cause to arrest the driver for drunk driving. FSTs fall into two categories: (1) Standardized FSTs under the National Highway Traffic Safety Administration (NHTSA); and (2) Non-standardized FSTs. The One Leg Stand test is a standardized field sobriety test under NHTSA.

What is the One Leg Stand Test?

Like the title of the test suggests, the One Leg Stand test involves balancing on one foot while the other foot is raised. It is considered a “divided attention” test, designed to test – among other things – cognitive skills, balance and coordination. Like other field sobriety tests, the One Leg Stand test is designed to determine whether or not the officer has probable cause to arrest a person for driving under the influence. However, the test will likely be used to show that the defendant was actually under the influence at the time of driving. Like all field sobriety tests, the best way to “pass” this test is to refuse to do the test.

How is the One Leg Stand Test Administered?

In the One Leg Stand test, the driver is instructed to stand with feet together with arms down at their sides. Then the driver is instructed to raise one foot approximately six inches off the ground. Then the driver counts out loud by thousands (one thousand-one, one thousand-two, etc.) until they’re told to put their foot down. The officer times the subject for 30 seconds. The ability to understand and follow instructions is, in and of itself, a part of the test.

During the test, the officer looks for four indicators of impairment:

Swaying while balancing. Swaying back and forth, or in a circular motion in a marked or distinct manner may indicate impairment.

Raising the arms to keep balance. Any raising of the arms over six inches may indicate impairment.

Hopping to maintain balance. While moving, the anchor foot may be used to balance if the subject raises the anchor foot off the ground. This movement may indicate impairment.

Putting the raised foot down. If the raised foot is placed on the ground, it may indicate impairment.

Is the One Leg Stand Test Accurate?

Because the One Leg Stand test is a standardized NHTSA test, there have been several studies performed to determine whether the One Leg Stand test is an accurate indicator of whether someone is impaired to the point of not being able to operate a vehicle safely. NHTSA has done two studies. The first study was done in 1981 and showed that the One Leg Stand test was only accurate 68% of the time in demonstrating that the person was over the legal limit. In 1981, the legal limit, however, was .10 BAC, not .08 BAC. That means the One Leg Stand test was not accurate for every one in three persons. In 1998, the studies showed that a person, who had made two or more of the indicators (explained above) in the One Leg Stand test, was 83% accurate in determining whether the person was above the legal limit. Although the results improved, the One Leg Stand test was inaccurate in nearly 1 in 5 individuals.

Like other coordination and balance field sobriety tests, various factors may influence the One Leg Stand test. Those individuals who are elderly, overweight, have leg or back injuries, or have illness or injury related to the inner ear may “fail” the One Leg Stand test even if completely sober. In addition, the ground upon which the test is done must be hard and flat, or otherwise it may skew the results. Similarly, women who are wearing high heels may also have difficulty with this test, even sober.